«The physiology of the lungs» Made by: Toktamyssova A. M. 1-008 gr

Plan The physiology of the lungs Gaseous Exchange Lung Volumes and Capacities Lung Rates and Terminology Peak Flow

The physiology of the lungs The lungs have an enormous surface area due to their physiological make-up. The trachea (windpipe) extends downward from the base of the larynx (voice box). Numerous cartilage rings strengthen the walls of the trachea – the cartilage also serves to keep the trachea open, allowing air to flow through on its way to the lungs. At its bottom end, the trachea divides into left and right air tubes called bronchi, which connect to the lungs. Within the lungs, the bronchi branch into smaller bronchi and even smaller tubes called bronchioles. Bronchioles, which are as thin as a strand of hair, end in tiny air sacs called alveoli, where the exchange of oxygen and carbon dioxide actually takes place. Each lung houses about 300 to 400 million alveoli. Estimates suggest the surface area of the lungs is equivalent to a tennis court!

Alveoly

When one breathes normally not all the alveoli and capillaries of the lungs are opened. When respiration becomes deep, the number of the opened alveoli and capillaries increases. The flow of blood into the lungs increases when one breathes in and it decreases when one breathes out.

Gaseous Exchange Gaseous exchange is the process where useful gases from the air are diffused into the bloodstream, and gases to be excreted are forced back into the lungs. The process occurs in the alveoli – the gases exchange over a tiny (one cell thick) membrane, with Oxygen passing into the bloodstream and waste Carbon Dioxide diffusing into the alveoli ready for excretion via exhalation.

Lung Volumes and Capacities Tidal Volume Tidal volume is the volume of inspired and expired air during normal breathing. The important point with tidal volume is that the breathing is as normal possible – the forced inspiration of expiration of air is a different term. An average figure for an adult male is around 500ml per breath. Inspiratory Reserve Volume Inspiratory Reserve Volume is the amount of air that can be inspired forcefully after the inspiration of the normal tidal volume. An average figure for an adult male is around 3000ml. Expiratory Reserve Volume Expiratory reserve volume is the amount of air that can be forcefully expired after expiration of the normal tidal volume. An average figure for an adult male is around 1100ml. Residual Volume Residual volume is the volume of air still remaining in the respiratory passages and lungs after the most forceful expiration. An average figure for an adult male is around 1200ml.

Inspiratory Capacity Inspiratory capacity is tidal volume plus inspiratory reserve volume (the amount of air a person can inspire after a normal expiration). An average figure for an adult male is around 3500ml. Functional Residual Capacity Functional residual capacity is the expiratory reserve volume plus the residual volume (the amount of air remaining in the lungs after a normal expiration). An average figure for an adult male is around 2300ml. Vital Capacity Vital capacity is the sum of the inspiratory reserve volume, the tidal volume and the expiratory reserve volume. Essentially this is the complete volume of useable space within the lungs. An average figure for an adult male is around 4600ml. Total Lung Capacity Total lung capacity is the sum of the inspiratory and expiratory reserve volumes plus the tidal volume and the residual volume. An average figure for an adult male is around 5800ml.

Lung Rates and Terminology Given the lungs direct link to breathing as a reflex, added to the importance to the body of correct lung function there are various terms and tests to ensure lung function is as it should be. Testing can highlight any potential problems or help to provide a clear diagnosis in the case of lung disease.

Oxygen Consumption Oxygen consumption is the total volume of oxygen inhaled minus the volume of oxygen exhaled. Carbon Dioxide Production Carbon dioxide production is the volume of carbon dioxide exhaled minus the volume of carbon dioxide inhaled.

Respiratory Rate Respiratory Rate is the number of breaths we take per minute. The method most often used to assess this is simply a counting of how many times per minute the chest rises and falls – the breathing reflex is centred entirely in the thoracic cavity and as such this is an accepted site to assess respiratory rate. An average figure for an adult male is 12-20 breaths per minute. Minute Ventilation Minute ventilation is the product of respiratory rate and tidal volume. Multiplying the frequency of breathing by the volume of the breaths provides a figure for the total amount of air moved in and out of the respiratory system each minute. An average figure for an adult male is between 6000ml and 10000ml.

Peak Flow Peak flow is a measure of how fast you can blow air out of your lungs. In so doing, it measures how wide the airways in your lungs are. For people with asthma, this simple test shows how well their asthma is being controlled. In normal populations, it tells us how well their lungs are functioning and make us aware of any potential problems before they become too serious. The airways can be narrowed for the following reasons: Their linings are swollen There is mucus in the airways The tubes are constricted by the special muscles surrounding the airways.

Literature http://www.hoylesfitness.com/physiology/1427/ “Essential english for medical students” A.M.Maslova